This application is the national phase under 35 U.S.C. xc2xa7371 of PCT International Application No. PCT/JP01/05015 which has an International filing date of Jun. 13, 2001, which designated the United States of America.
The present invention relates to a simulating method for vehicle/tire performances that is useful for effectively developing a tire suitable for a vehicle.
In the case of developing a tire suitable for a specific vehicle, conventionally, a tire is actually made by way of trial and mounted on the vehicle and various kinds of evaluations such as sensory evaluation, instrumental evaluation and the like are made by actually running the vehicle. Further, the trial tire is subjected to laboratory tests using a drum tester for cornering property and the like. Then, according to the results thereof, the test model is improved and again subjected to the actual car evaluations by mounting it on the vehicle model. Thus, there are repeatedly made the actual car evaluations using the actual car.
However, in the conventional developing method in which the actual car evaluations are made, a lot of trouble and labor and much time are required because the tires must be actually made and it is necessary to prepare the vehicle used in the actual car test, a place for running the vehicle, measuring devices, operators therefor, a test driver and the like.
The present invention was therefore, made by taking the above mentioned problems into consideration, and an object thereof is to provide a simulating method for vehicle/tire performances, in which vehicle""s traveling properties and/or tire properties can be estimated by running a vehicle model virtually by means of computer or the like, which vehicle model is obtained by modeling the vehicle""s main body, suspension members, tires and the like by using elements which can be treated in a finite element method, and by which a tire suitable for the vehicle can be effectively developed for a short time.
In accordance with the present invention, a simulating method for vehicle/tire performances is characterized in that the method comprises: a tire model preparing step of preparing a tire model in which a tire, inclusive of a ply, is divided into a finite number of elements; a vehicle body model preparing step of preparing a vehicle body model in which a vehicle body, inclusive of suspension members, is divided into a finite number of elements; a vehicle model preparing step of preparing a vehicle model of the vehicle by attaching the tire model to a suspension model of the suspension members in the vehicle body model; and a simulation step of simulating traveling of the vehicle model under a given boundary condition and obtaining vehicle""s traveling properties and/or a tire""s property.
The above-mentioned vehicle""s traveling properties may include at least one of the degree of understeer and oversteer, the vehicle""s response speed to steering and the degree of the vehicle""s roll. The above-mentioned suspension members include an arm, spring, shock absorber, torsion beam, stabilizer, link rod and rubber bush. The arm and link rod can be modeled by a rigid beam element. The spring, shock absorber and rubber bush can be modeled by a linear or non-linear spring element. The torsion beam and stabilizer can be modeled by a torsional beam element.
Further, a vibrating property of the vehicle body under 10 Hz may be included as one of the vehicle""s traveling properties. In this case, it is desirable that the vehicle body model is a rigid model that does not deform.
Furthermore, a vibrating property of the vehicle body between 10 Hz and 100 Hz may be included as one of the vehicle""s traveling properties. In this case, it is preferable that the vehicle body model exclusive of the suspension model is provided with a vibration mode substantially same as the vibration mode of the vehicle body to be estimated.
The traveling simulation is made by running the vehicle model on a road model of a road surface made by elements. For example, the road model can be made out of a rigid element and a water element for water thereon, whereby it is possible to estimate wet traveling properties as the above-mentioned vehicle""s traveling properties.
Further, the road model can be made of a rigid element and a snow element for snow thereon, whereby it is possible to estimate on the-snow traveling properties as the vehicle""s traveling properties.
Furthermore, the road model can be made out of a rigid element and a mud element for mud thereon, whereby it is possible to estimate traveling properties on muddy roads as the vehicle""s traveling properties.
Still furthermore, the road model can be made of a rigid element and a sand element for sand thereon, whereby it is possible to estimate traveling properties on sandy roads as the vehicle""s traveling properties.
Incidentally, the road model may be defined as being entirely flat but it can include an uneven part, whereby it is possible to estimate ride comfort as the vehicle""s traveling properties.
The above-mentioned vehicle model preparing step preferably includes: setting an internal pressure condition to the tire model under a gravitational condition of 0 G; and applying a load of the vehicle body model to the tire model by setting the gravitational condition to 1 G after setting the internal pressure condition to the tire model.
In the above-mentioned simulation step, it is possible to use the vehicle model having an initial speed v (not equal to zero). In this case, a speed corresponding to the translational component of the initial speed v is given to the vehicle body model, but given to the tire model are the translational component of the initial speed v and a speed corresponding to a rotational component.
Further, the above-mentioned traveling simulation may include a steady circling simulation in which the vehicle model circles with the steering angle of the tire model fixed. In this case, a steering property can be estimated on the basis of the turning radius of the vehicle model and/or the roll angle of the vehicle model which are obtained by the steady circling simulation as the vehicle""s traveling properties.
Furthermore, the traveling simulation may include a lane change simulation in which the state at the time of a lane change is simulated. In this case, as one of the vehicle""s traveling properties, a lane change property can be estimated on the basis of a behavior of the vehicle model and/or a convergence at a time of returning back the steering angle of the vehicle model, which are obtained by the lane change simulation.
Still furthermore, the traveling simulation may include a driving simulation in which a constant torque is applied to the tire model and a speed change of the vehicle model is observed. In this case, it is possible to estimate a driving force property as one of the vehicle""s traveling properties.
Furthermore, the traveling simulation may include a braking simulation in which a constant braking force is applied to the tire model and a speed change of the vehicle model is observed. In this case, it is possible to estimate a braking force property as one of the vehicle""s traveling properties.